In certain operations involving numerical control machines for drilling, cutting, milling and grinding operations, it is desirable to have a device which can control the depth of the cut of the tool in the workpiece independent of the numerical control machine. This improved hydraulic stop is designed for use where the exact location of the surface of the workpiece is unknown with respect to the program start point of a numerical control machine. The improved hydraulic stop limits penetration of the cutter and also provides a safety device to assure unit will collapse at a safe pressure if override mechansim should fail.
Prior art hydraulic stop covered by U.S. Pat. No. 4,273,481 could be used to limit penetration of a drill bit. This improved hydraulic stop has reduced complexity and size. The reduction in size results in a shorter, more rigid tool, with improved tool concentricity.